Erosion, Corrosion Water Hammer and Leaks in Economizer

Economizer is one of heat exchanger equipment in steam boiler that absorbs heat from flue gas then transfers it to feedwater. Economizer can help steam boiler to increase efficiency. Some of failure regarding to operation of economizer can be occur because of erosion, corrosion, water hammer and leaks. So, the preventive maintenance should be performed.

Possibility of corrosion can be occur if there is concentration of oxygen either high or low concentration. Corrosion can be prevented by removing oxygen content in feedwater. Deaerator has important role to make feedwater free from oxygen.

Steam boiler which uses coal as fuel combustion will has a lot of fly ash particle. It will impact to metal tube erosion even steam boiler is operated with high excess air and on maximum continuous rating; possibility of erosion is highly occur. If certain amount of fly ash is localized in certain area then forming plugging, this condition will reduce flow area and increase the velocity of flue gas, so potential erosion on economizer tubes will mostly occur and the result economizer tubes will leak and rupture. Preventive maintenance to clean plug and fly ash attached on surface tube must be executed routinely. Rotary soot blower type is suitable applied to this preventive maintenance in economizer.

Another warning regarding to economizer operation is water hammer. At certain condition, level water gauge can not read water level in steam drum correctly, the result is boiler control allow feedwater is not distributed into steam drum for a while. So steam will flow enter and become trapped in economizer. When feedwater is distributed again through economizer although with low pressure, it will impact to water hammer because of steam is encountered immediately with feedwater on certain pressure. To overcome this condition, venting should be installed to make the steam out from economizer or supply feedwater constantly.

No comments: